It's a striking opening: Dante is waiting for his A-level results to arrive in the post, but what he gets instead is an ex-girlfriend on the doorstop with a baby she says is his. One event offers him a future at university; the other, since the mother is about to dump the baby on him, leads to the death of all his dreams.

So, a strong start and an unusual perspective on teenage pregnancy in the UK. Dante and Melanie had only one drunken sexual episode at a party, and baby Emma is the result. But Melanie didn't tell Dante she was pregnant; she just left school and faded out of his life. At the beginning of the book, Dante has a new girlfriend, Collette, and Melanie's arrival out of the blue couldn't be worse timing.

Her goal, achieved by a mean trick, of leaving the baby in Dante's care, leads to a nightmare scenario – at least, most 17-year-old boys would see it that way. A screaming Emma in a pushchair, a bag of nappies and babyfood and a disappearing mother who has blocked his number from her mobile phone. And Dante has to tell his father whose baby this is.

Dad Tyler has experience of single fatherhood himself, because Dante's mother has died of cancer. But his reaction to his unexpected granddaughter is the predictable: "You stupid bloody idiot." The third male in this set-up is Adam, Dante's younger brother, who is comfortably gay and out, though neither of the other two members of the family acknowledges it.

Adam takes to baby Emma immediately and Dad takes care of the practical issues, buying her a cot, clothes and "three-quarters of the contents of the baby store he'd been to". Meanwhile Dante hits the computer to find out about DNA tests. He is horrified that Emma's cot is placed at the bottom of his bed; he feels nothing for her except shock at her existence and horror that his future has so changed in a matter of hours.

It's an immensely readable book, as you would expect from Malorie Blackman, and the account of how Dante comes to terms with fatherhood and his responsibilities is genuinely moving, while staying on the right side of sentimentality. Along the way he also accepts his brother's orientation, though at a terrible cost.

The struggles of raising an 11-month-baby are not underestimated and Dante has quite a journey to make, from the boy who takes her in a sling to his exam results' celebration in a bar – bad idea, since Collette is there – to the man who stands up to a social worker who thinks he isn't coping.

It's only about seven-eighths of the way through that you realise, from a throwaway remark, that Dante and his brother are black. This is clever – as is the cover image, which gives nothing away – but for me raised questions the book couldn't answer. What about their parents? And Melanie? Society isn't colour-blind yet and it really would be an issue, especially with that stereotypical social worker.

Blackman is a clever sleight-of-hand artist. It's only after you've finished reading that some doubts creep in. Who today waits for their results in the post or postpones their celebrations to the Friday night? Every teenager I know expects to meet up with mates on the Thursday night regardless of possible work next day. Then you wonder if that striking opening was manipulated just to provide the contrast of the two destinies calling at the door. But in spite of these reservations, it's a good book and a great story.